Philomedes assimilis Brady, 1907

Chavtur, Vladimir G. & Keyser, Dietmar, 2016, Benthic myodocopid Ostracoda (Philomedidae) from the Southern Ocean, Zootaxa 4141 (1), pp. 1-70 : 28-37

Philomedes assimilis Brady, 1907

( Figs. 17–22 )

1907 Philomedes assimilis Brady ,: 5, pl. 1, Figs. 16–21 , pl. 2, Figs, 1–6. 1908 Philomedes assimilis Brady 1907 —Müller: 87, pl. 6: Figs. 9–17 ; pl. 7: Figs. 14–16 . 1912 Philomedes assimilis Brady 1907 —Müller: 26 [key], 31.

1912 Philomedes assimilis Brady 1907 —Scott: 586.

1920 Philomedes assimilis Brady 1907 —Skogsberg: 352, 413.

1921 Philomedes assimilis Brady 1907 —Barney: 178.

1967 Philomedes assimilis Brady 1907 —Lofthouse: 143

1971 Philomedes assimilis Brady 1907 —Kornicker: 186, Fig. 14 . 1975 Philomedes assimilis Brady 1907 —Kornicker: 229–236, Figs. 128–130, 131, 132 (map). 1991 Philomedes assimilis Brady 1907 —Hartmann: 212.

1986 Philomedes cf. P. assimilis Brady 1907 —Hartmann: 235.

1907 Philomedes antarctica Brady : 5, pl. 5, Figs. 1–10 .

1971 Philomedes antarctica Brady, 1907 —Kornicker: 189, Fig. 15 .?1990 P. heptathrix Kornicker, 1975 —Hartmann: 199, Abb. 1.

Studied material (coordinates, depth and sediment see Appendix). 16th Soviet (=Russian) Antarctic Expedition, sample 161: MIMB 18286—adult female (2.05 mm).

Sample 162: MIMB 18 287 and 18288—2 adult females (2.15 mm, other is deformed).

Sample 164: MIMB 18 291—adult male (2.16 mm).

Sample—unknown (depth 45 m), 18 February1972; MIMB 18293—adult male (2.30 mm).

Sample 166: MIMB 18 295—immature male (1.90 mm).

Sample 169: MIMB 18 292—adult male (2.05 mm); MIMB 18289—adult female (1.92 mm).

34th Soviet (=Russian) Antarctic Expedition, station 10, sample 1: MIMB 18294—adult male (2.10 mm).

RV “Polarstern”, ANT XIII/3, station 39/02: ZMH-K-42264—adult female (1.97 mm) and ZMH-K-42265— adult male (2.24 mm).

52th Russian Antarctic Expedition, station 8, sample 37: MIMB 18290—adult female (2.02 mm).

Additional material. See Appendix.

Diagnosis of female ( Kornicker 1975, with additional remarks). Carapace: with truncate posterior and angular caudal process, length 1.67–2.15 mm.

First antenna: 2nd joint with 5–7 setae, 3–4 ventral, 1 lateral and 1–2 dorsal.

Second antenna: 1st joint of endopodite with 5–6 setae, 4–5 proximal and 1 distal; 2nd joint with 1 long and 3 short ventral setae and 1 long recurved terminal seta.

Mandible: dorsal margin of basale with 4–6 setae, 2–4 near middle and 2 subterminal.

Sixth limb: epipodite with 3–5 setae.

Seventh limb: each limb with 8–10 (usually 9) setae, 4–5 distal and 3–5 proximal; 1–2 pegs present on opposite terminal comb.

Caudal furca: each lamella with 10 (very rarely 9) claws.

Bellonci organ: 1-jointed, with rounded tip.

Lateral eye: small with 2 divided ommatidia.

Anterior process (above upper lip): relatively developed and with rounded tip.

Diagnosis of male. Carapace: length 2.12–2.25 mm.

First antenna: 2nd joint with 4–5 setae, 2–3 ventral, 1 lateral and 1–2 dorsal.

Second antenna: 1st joint of endopodite with 6 seta, 5 proximal and 1 distal; proximal seta of 3rd joint somewhat longer than half of its length.

Mandible: dorsal margin of basale with 4 setae, 2 near middle and 2 subterminal; coxale endite present.

Sixth limb: epipodite with 3 (rarely with 2) setae.

Seventh limb: each limb with 8–10 (usually with 9) setae, 4–5 distal and 4–5 proximal; 2 pegs present on opposite terminal comb.

Caudal furca: each lamella with 9 (rarely with 10) claws.

Bellonci organ: 1-jointed, with rounded tip.

Anterior process (above upper lip): relatively developed with rounded tip.

Supplementary description of adult female. Carapace ( Figs. 17 A–L, R–T; 18 A–C). Length 1.67–2.15 mm (in literature: 1.67–2.0 mm). Shape of carapace very various ( Fig. 17 ). Infold on rostrum with about 13–28 setae forming a vertical row and on incisure with 3–4 setae near margin. Anterior-ventral inside with about 10–34 short setae and with 13–15 striations. Infold on caudal process with 3–11 short setae.

First antenna ( Fig. 18 D, H). First joint with 4–5 setae in proximal group and 1 distal seta. Second joint with 5–7 setae, 1–2 dorsal, 1 lateral and 3 or 4 ventral.

Second antenna ( Fig. 18 I–L). Length of setae (1 long and 3 short ventral and 1 subterminal setae) on second endopodite joint varying.

Mandible ( Fig. 21 F). Basale: dorsal margin with 4–6 setae, 2–4 near middle and subterminal setae; medial side with 6 setae, 3 pectinate and 3 normal; lateral surface with 4–5 setae forming a row parallel to ventral margin; ventral margin with 3–4 distal setae. Endopodite: first joint with 3–4 ventral setae; dorsal margin of second joint with 2 setae in proximal group, 6 setae in distal group and 1 seta between these groups, ventral margin with 2–3 setae in subterminal group and 3 setae in terminal group.

Sixth limb. Endite I with 2–3 terminal and 1 medial setae, endite II with 3 terminal and 1 medial setae, endite III with 8–9 terminal and 1 medial setae, endite IV with 7–8 terminal and 1 medial setae, end joint with 24–30 setae, 3–5 setae present in place of epipodial appendage.

Seventh limb. Each limb with 8–10 setae, 4–6 distal (usually 2+3, rarely 2+2 and 3+3) and 4–5 setae (usually 2+2, rarely 3+2 and 1+3); each seta with 2–5 bells. Terminal comb with 10–11 teeth; 1–2 pegs present opposite comb.

Caudal furca. Each lamella usually with 10 claws and rarely 9 claws.

Bellonci organ ( Fig. 18 D, E). 1-jointed, with rounded tip.

Upper lip ( Figs. 18 D, F, G; 20 H). Lip ventrally hirsute and with several glandular processes at tip.

Anterior process of body ( Figs. 18 D, F, G; 20 H). Relatively large and rounded.

Supplementary description of adult male. Carapace ( Fig. 19 A–I): Length 2.12–2.25 mm (in literature: 2.12–2.24 mm). Shape of carapace variable ( Fig. 19 A–E). Infold on rostrum with about 17–18 setae forming a row. Antero-ventral inside with about 11–15 spine-like setae. Infold on caudal process with 4–6 spine-like setae. First antenna ( Figs. 19 L; 20 E–G; 22 A–H). Second joint with 4–5 setae, 1 dorsal, 1 lateral and 2–3 ventral setae; length of setae varying ( Fig. 22 A–H). Sensory seta on fifth joint evenly tapered from base to tip (without knee in middle) and with 5 terminal filaments ( Fig. 20 I).

Second antenna ( Figs. 20 J; 21 A–D). First endopodial joint with 6 setae, 5 proximal and 1 distal; second joint with 2 muscle bands, one extends from first joint to proximal margin of third joint and other from middle of dorsal margin of second joint to proximal margin of third joint ( Fig. 21 D). Proximal seta of third joint slightly longer than half of its length.

Mandible ( Fig. 21 E, G). Coxale endite bifurcate distally. Basale: dorsal margin with 4 setae, 2 near middle and 2 subterminal setae; medial side with 6 setae; lateral surface with 4 setae forming a row parallel to the ventral margin; ventral margin with 3 distal setae. Endopodite: first joint with 4 or 5 ventral setae; dorsal margin of second joint with 2 setae in proximal group, 6 setae in distal group and 1 seta between these groups, and ventral margin with 2–3 setae in subterminal group and 3 setae in terminal group.

Sixth limb. Endite I with 1–2 terminal and 1–2 medial setae; endite II with 2–3 terminal and 1 medial setae; endite III with 7–8 terminal and 1 medial setae; endite IV with 7–8 terminal and 1 medial setae; end joint with 21 setae (in all studied females); 2–3 setae present in place of epipodial appendage.

Seventh limb ( Fig. 21 H). Each limb with 8–10 setae, 4–5 distal (2+3 or 2+2) and 4–5 proximal (2+3 or 2+2); each seta with 3–6 bells. Terminal comb with 10 teeth; 2 pegs present on opposite comb.

Caudal furca ( Fig. 22 K–N). Limb with 9+9 or 9+10 claws.

Copulatory appendage ( Fig. 22 K–N). Elongate, with 2 lobes (long and short). Length of appendage varying, about half to 9/10 length of lamella of furca.

Medial eye ( Fig. 20 A–G). Large, usual smooth (only in female ( Fig. 20 C, G) eye with 3 anterior sclerotic tubercles.).

Bellonci organ ( Figs. 19 K, 20 A–G). Elongate, unsegmented, with rounded tip and subequal, slightly longer, or shorter than length of first joint of first antenna.

Upper lip ( Fig. 20 E–G). Tip with several glandular processes.

Anterior process of body ( Fig. 20 E–G). Small or midsize and rounded.

Supplementary of A-1 male. Length 1.75 mm.

First antenna. Second joint with 1 dorsal, 1 lateral and 2 ventral setae; third joint with 2 dorsal and 1 ventral setae; fourth joint with 1 dorsal and 3 ventral setae.

Second antenna ( Fig. 22 I, J). First joint with 6 setae, 5 proximal and 1 distal; second joint with 1 long spinous and 2 short ventral setae; third joint with 1 long dorsal and 2 short terminal setae.

Mandible. Similar to that of adult female.

Sixth limb. 4 setae present in place of epipodial appendage.

Seventh limb. Each limb with 9 setae (2+3 distal and 2+2 proximal). Terminal comb with 9 teeth; 1 peg present on opposite comb.

Caudal furca. Each lamella with 9 claws.

Distribution and ecology. Circumantarctic sublitoral-bathyal species. It has been collected almost around the whole Antarctic continent between 62° and 78°S (as rule to south of 65–66° S ( Fig. 16 )) at depths of 7 to 876 m, temperature range of 0.57° to -1.53°C and on hard and soft substrates: rock, stone, gravel, sand, muddy sand ( Brady 1907; Kornicker 1971, 1975; Hartmann 1989).

Figures

FIGURE 1. Distribution map of species of the family Philomedidae in the Antarctic region and adjacent regions from literature and original data.

FIGURE 2. Distribution map of Scleroconcha gallardoi, S. tuberculata sp. nov., and S. species indet.

FIGURE 3. Scleroconcha tuberculata sp. nov. (Female: A, C—MIMB 18275; B, D, E, G—MIMB 18270; F—MIMB 18271; H, J—MIMB 18269; I, K—MIMB 18272). A, B—left valve of carapace in lateral and inside views; C—carapace in ventral view; D—detail of antero-ventral infold of left valve (marginal setae cut); E—detail of setae on left valve, lateral view; F – Idistal part of Bellonci organ; J, K—endopodite of 2 nd antenna.

FIGURE 4. Scleroconcha tuberculata sp. nov. (Female: A, G, I—MIMB 18269; B, F—MIMB 18272; C, D, H—MIMB 18270; E—MIMB 18271). A, B—upper lip, anterior process, medial eye and Bellonci organ; C—medial eye and Bellonci organ; D-G—medial eye and base of Bellonci organ; H—upper lip and anterior process, I—lateral eye.

FIGURE 5. Scleroconcha tuberculata sp. nov. (Female: A, B, D, F, H, J—MIMB 18269; C, I, K— 18272; E, G— 18271; L— MIMB 18270). A—mandible (not all setae shown); B-C—exopodite and details of 1 st endopodial joint and basale of mandible; D—dorsal margin of 2 nd endopodial joint of mandible; E-F—exopodite and detail of 1 st endopodial joint of mandible; G-Ldetail of 2 nd exopodial joint of 5 th limb.

FIGURE 6. Scleroconcha tuberculata sp. nov. (Female: A, C—MIMB 18271; B, D, H—MIMB 18272; E, F—MIMB 18269; G—MIMB 18270). A—exopodial joints 1 – 5 of 5 th limb; B – G—tip of 7 th limb; H—detail of caudal furca.

FIGURE 7. Scleroconcha tuberculata sp. nov. (Male: MIMB 18268). A, B—right and left valve of carapace in lateral view; C—carapace in ventral view; D—rostrum in lateral view; E—infold of rostrum; F—infold of rostrum and anterior detail of carapace; G—pits of middle right valve; H—upper lip, anterior process, medial eye and Bellonci organ; I—distal part of Bellonci organ; J—medial eye and base of Bellonci organ.

FIGURE 8. Scleroconcha tuberculata sp. nov. (Male: MIMB 18268). 2 nd antenna: A—exopodial joint 3 – 9 (setae not shown); B—exopodial joints 1 – 3; C, D—endopodite of left and right limb; E—detail of 3 rd endopodial joint; F— 1 st endopodial joint. Mandible: G, H—basale, exopodite (abnormal on left limb) and endopodite (setae shown only for basale); I—endite of coxale.

FIGURE 9. Scleroconcha tuberculata sp. nov. (Male: MIMB 18268). A, B—exopodite (abnormal on left limb), 1 st endopodial joint and detail of basale; C, D— 2 nd and 3 rd endopodial joints; E—tip of 7 th limb; F—detail of caudal furca; G—lateral eye.

FIGURE 10. Scleroconcha tuberculata sp. nov. (Immature male: A, D, I – L—MIMB 18273; B—MIMB 18274; C, E—ZMH- K- 42259; F—ZMH-K- 42260. Immature female: G, H—ZMH-K- 42261). A – C—left valves of carapace in lateral view; D – Gright valves in lateral view (for panel D ribs not shown); H—carapace in ventral view; I—upper lip, anterior process, medial eye and Bellonci organ; J, K—endopodite of 2 nd antenna; L—tip of 7 th limb.

FIGURE 11. Scleroconcha tuberculata sp. nov. (Immature female: A, B—ZMH-K- 42262; immature male: C – J—ZMH-K- 42259). A—left valve of carapace in lateral view; B—carapace in ventral view; C—infold of rostrum and detail of anterior margin; D, E—infold of caudal process of right valve; F— 1 st and 2 nd joints of 1 st antenna, medial eye and Bellonci organ; Gendopodite and details of protopodite and exopodite of 2 nd antenna; I, H—tip of 3 rd endopodial joint of 2 nd antenna; J—ventroproximal detail of mandible basale.

FIGURE 12. Scleroconcha gallardoi (Female: A, E—MIMB 18281; B, D, F, G— 18277; C—MIMB 18277; H – J—MIMB 18280; K—MIMB 18276). Carapace: A, D—right valve in lateral and inside view; B, C—left valve in lateral view; E, Gcarapace in ventral view; F—carapace in dorsal view; H—infold of rostrum; I—infold of anterior part; J—ornamentation and setae of middle valve in lateral view; K—upper lip and anterior process.

FIGURE 13. Scleroconcha gallardoi (Female: A, F—MIMB 18276; B, D, G, H—MIMB 18277; C, E—MIMB 18280). A— 1 st, 2 nd and 3 rd joint of 1 st antenna, medial eye and Bellonci organ; B—upper lip, anterior process, medial eye and Bellonci organ; C – F—endopodite of 2 nd antenna; G, H—basale, exopodite and 1 st endopodial joint of mandible.

FIGURE 14. Scleroconcha gallardoi (Immature female: A, C—MIMB 18282; immature male: B, D—MIMB 18283; female: E – G—MIMB 18279). A, B—right valve of carapace in lateral view; C, D—left valve in lateral view; E, F— 6 th limb (not all setae shown; abnormal end joint on panel F); G—abnormal joint of 6 th limb.

FIGURE 15. Scleroconcha gallardoi (Immature male: A – F, H, I—MIMB 18283; female: G—MIMB 18279), S. species (Juvenile: J—MIMB 18285). A—upper lip, anterior process, medial eye and Bellonci organ; B—distal part of Bellonci organ; C— 1 st and 2 nd joint of 1 st antenna (setae not shown) and lateral eye. 2 nd antenna: D—endopodite; E— 1 st and 2 nd endopodial joints; F— 2 nd and 3 rd joint. G – I—tip of 7 th limb. J—left valve of carapace.

FIGURE 16. Distribution map of Philomedes assimilis.

FIGURE 17. Philomedes assimilis (Female: A—MIMB 18289; B, J— 16 th SAE (Soviet Antarctic Expedition), 18.02. 1972, sample 161; C, G, H, Q— 34 th SAE, 17.01. 1989, St. 10, sample 1; D, E, I, K— 34 th SAE, 3.02. 1989, St. 15, sample 2; F—ZMH- K- 42264; L— 52 th R (Russian) AE, 4.01. 2007, St. 6, sample 28; M—MIMB 18290; R—MIMB 18287; S—MIMB 18288; T— 16 th SAE, 17.02. 1972, Station—unknown. Immature female: N – P— 52 th RAE, 5.01. 2007, St. 7, sample 36). A – P—left valve of carapace in lateral view; Q – T—right valve in lateral view.

FIGURE 18. Philomedes assimilis (Female: A – C—MIMB 18286; D, F, H – J—MIMB 18287; E, G, K, L—ZMH-K- 42264). A, B—setae on rostrum and caudal process of carapace in lateral view; C—detail of ornamentation and setae on central surface of right valve; D—upper lip, anterior process, medial eye, Bellonci organ and 1 st and 2 nd joints of 1 st antenna; E—Bellonci organ; F, G—upper lip and anterior process; H— 2 nd joint of 1 st antenna; I – L—endopodite of 2 nd antenna.

FIGURE 19. Philomedes assimilis (Male: A, J—MIMB 18293; B—MIMB 18294; C, H, I—ZMH-K- 42265; D, F, G—MIMB 18291; E—MIMB 18292. Female: K, L—MIMB 18288). Carapace: A – D—left valve in lateral view; E—right valve in lateral view; F—infold of rostrum and antero-ventral part of left valve; G, H—infold of caudal process; I—area on left valve, lateral view. J—lateral eye; K—Bellonci organ; L— 2 nd joint of 1 st antenna.

FIGURE 20. Philomedes assimilis (Male: A, E—MIMB 18291; B, I—MIMB 18292; C, G, J—MIMB 18293; D, F—ZMH-K- 42265. Female: H—MIMB 18288). A – D—medial eye and Bellonci organ; E, F, G—upper lip, anterior process, medial and lateral (not shown on panel G) eyes, Bellonci organ, 1 st and 2 nd joints of 1 st antenna; H—upper lip and anterior process; I—seta of 5 th joint of 1 st antenna; J— 1 st endopodial joint of 2 nd antenna.

FIGURE 21. Philomedes assimilis (Male: A, H—MIMB 18291; B, E, G—ZMH-K- 42265; C, D—MIMB 18292; Female: F— MIMB 18288). A – D—endopodite of 2 nd antenna; E—basale, exopodite, endopodite of mandible; F—basale, exopodite and 1 st endopodial joint of mandible; G—coxal endite of mandible; H—tip of 7 th limb.

FIGURE 22. Philomedes assimilis (Male: A, B, K—MIMB 18291; C, D, N—MIMB 18293; E, F, L—ZMH-K- 42265; G, H, M—MIMB 18292. Immature male: I, J—MIMB 18295). A – H— 1 st joint of 1 st antenna; I—endopodite of 2 nd antenna; J— 3 rd endopodial joint of 2 nd antenna; K – N—copulatory appendage and caudal furca.